Inflammatory mediators in BAL fluid as markers of evolving pneumonia in leukocytopenic patients

Effects of polysaccharide intercellular adhesin (PIA) in an ex vivo model of whole blood killing and in prosthetic joint infection (PJI): A role for C5a

BACKGROUND

A major complication of using medical devices is the development of biofilm-associated infection caused by Staphylococcus epidermidis where polysaccharide intercellular adhesin (PIA) is a major mechanism of biofilm accumulation. PIA affects innate and humoral immunity in isolated cells and animal models. Few studies have examined these effects in prosthetic joint infection (PJI).

METHODS

This study used ex vivo whole blood modelling in controls together with matched-serum and staphylococcal isolates from patients with PJI.

RESULTS

Whole blood killing of PIA positive S. epidermidis and its isogenic negative mutant was identical. Differences were unmasked in immunosuppressed whole blood pre-treated with dexamethasone where PIA positive bacteria showed a more resistant phenotype. PIA expression was identified in three unique patterns associated with bacteria and leukocytes, implicating a soluble form of PIA. Purified PIA reduced whole blood killing while increasing C5a levels. In clinically relevant staphylococcal isolates and serum samples from PJI patients; firstly complement C5a was increased 3-fold compared to controls; secondly, the C5a levels were significantly higher in serum from PJI patients whose isolates preferentially formed PIA-associated biofilms.

CONCLUSIONS

These data demonstrate for the first time that the biological effects of PIA are mediated through C5a in patients with PJI.

Diagnostic yield of bronchoscopy with bronchoalveolar lavage in febrile patients with hematologic malignancies and pulmonary infiltrates

Infectious complications are a major cause of morbidity and mortality in immunosuppressed patients. Febrile patients with hematologic malignancies and pulmonary infiltrates have high mortality rates, especially if mechanical ventilation is required. The diagnostic value of fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) in these patients is controversial. We retrospectively analyzed the microbiological results of BAL samples obtained during 249 FOB examinations from 199 febrile patients with hematologic malignancies and pulmonary infiltrates (underlying diseases: acute leukemia 103 patients, lymphoma 84 patients, other malignancies 12 patients). Two hundred forty-six examinations could be evaluated. Seventy-three out of 246 BAL samples were sterile; 55 samples showed microbiological findings classified as contamination or colonization. One hundred eighteen samples showed positive microbiological results of bacteria and/or fungi classified as causative pathogens. Thereof, in 70 samples, only bacterial pathogens were detectable (Gram-positive, 35; Gram-negative, 30; mixed Gram-positive and Gram-negative, 5). Thirteen samples showed both fungi and bacterial pathogens. In 33 samples, only fungi were detectable, thereof, in 15 samples Aspergillus species, in 16 samples Candida species, and in 2 both. In two samples, a viral pathogen could be detected. Three nonlethal complications (bleeding, arrhythmia) occurred that required early termination of FOB. In 94 (38.2%) patient episodes, antibiotic treatment was modified as a result of microbiological findings in BAL samples. Our results show that FOB with BAL is a valuable diagnostic tool with low complication rates in high-risk febrile patients with hematologic malignancies and pulmonary infiltrates, contributing crucial results for the individual case, and also improving epidemiologic knowledge.

Aerosolized ceftazidime for prevention of ventilator-associated pneumonia and drug effects on the proinflammatory response in critically ill trauma patients

STUDY OBJECTIVES

To evaluate the safety and efficacy of aerosolized ceftazidime for prevention of ventilator-associated pneumonia (VAP) and to evaluate the effects of the drug on the proinflammatory response.

DESIGN

Prospective, randomized, double-blind, placebo-controlled clinical trial.

SETTING

University teaching hospital.

PATIENTS

Forty critically ill trauma patients at high risk for VAP Intervention. Within 48 hours of admission to the intensive care unit (ICU), patients were randomly assigned to receive aerosolized ceftazidime 250 mg every 12 hours or placebo (normal saline) for up to 7 days. Bronchoalveolar concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, and IL-8 were determined at baseline and the end of therapy (days 4-7).

MEASUREMENTS AND MAIN RESULTS

The frequency of VAP in patients receiving aerosolized ceftazidime was 73% lower than that in patients receiving placebo at ICU day 14 (15% vs 55%, p = 0.021), and 54% lower for the entire ICU stay (30% vs 65%, p = 0.022). No clinically significant changes in bacterial culture and sensitivity patterns were observed. No adverse events from aerosolized ceftazidime were reported. Pulmonary TNF-alpha, IL-beta, and IL-8 concentrations were attenuated in the ceftazidime group compared with those in the placebo group (p < 0.001, p = 0.02, and p = 0.003). The frequency of VAP was related directly to changes in TNF-alpha and IL-beta (p < 0.001, p = 0.02).

CONCLUSIONS

Aerosolized ceftazidime decreased the frequency of VAP in critically ill trauma patients, without adversely affecting ICU flora. Aerosolized ceftazidime also may attenuate the proinflammatory response in the lung.

C5a delays apoptosis of human neutrophils by a phosphatidylinositol 3-kinase-signaling pathway

BACKGROUND

Studies have shown that survival factors including cytokines and growth factors delay apoptosis of human neutrophils via induction of the phosphatidylinositol-3 kinase (PI 3-K)/Akt pathway. In the present study, we explored whether complement fragment C5a has a modulatory effect on neutrophil apoptosis through this signaling pathway.

METHODS

Human neutrophils were isolated and treated with C5a for up to 24 hours, with or without wortmannin, a PI 3-K inhibitor, and staurosporine, a caspase-9 activator. Apoptosis was quantified by flow cytometry, using propidium iodide nuclear staining, and confirmed by the detection of DNA fragmentation on gel electrophoresis. PI 3-K downstream signaling events were evaluated by measuring the expression of cytosolic total and phosphorylated Akt and Bad proteins by Western blot analyses, and caspase-9 activity.

RESULTS

C5a inhibited neutrophil apoptosis in a dose- and time-dependent manner. The anti-apoptotic effects of C5a were markedly abrogated in the presence of wortmannin. Brief stimulation of neutrophils with C5a induced phosphorylation of Akt and Bad proteins through a PI 3-K-dependent pathway. Caspase-9 activity was minimal in C5a-treated cells, but markedly increased following PI 3-K inhibition by wortmannin. Finally, C5a reduced caspase-9 activity in staurosporine-treated cells.

CONCLUSIONS

This study demonstrates that C5a inhibits neutrophil apoptosis via a PI 3-K signaling pathway. This effect may be an important mechanism that improves cell survival and function in the inflammatory milieu.